1. Field of the Invention
The present invention relates to a pulse radar system using a millimeter wave band or a quasi-millimeter wave band, and particularly to a pulse radar system capable of measuring a distance by improving distance resolution or a S/N ratio with respect to a reflective wave from an obstacle at a short distance and a reflective wave from an obstacle at a long distance.
2. Description of the Related Art
There are pulse radar systems detecting the distance to an obstacle by transmitting a pulse wave and receiving the pulse wave reflected from the obstacle in related arts. In the pulse radar systems, a round-trip distance to an obstacle can be found by multiplying the time that elapses from the radiation of a transmission pulse wave to the reception of a reception pulse wave reflected from the obstacle, by light velocity.
Such a pulse radar system measures distances to obstacles at various distances from short distances to long distances; therefore, for the purpose of measuring an obstacle at a short distance, it is necessary to reduce the pulse width of a transmission pulse wave, so a reception system having a wide dynamic range is necessary. Thereby, there is an issue that the pulse radar system becomes complicated, and costs are increased.
In order to overcome the issue, there has been disclosed a technique of applying an AGC (Automatic Gain Control) circuit to the reception system (for example, refer to Japanese Unexamined Patent Application Publication No. H6-174826).